Apparatus for controlling air flow



June 23, 1942.

R. w. BECKETT APPARATUS CONTROLLING AIR FLOW Filed Feb 5, 1940 3 Sheets-Sheet 1 No R mm mm W LH INVEN TOR REGI'NALD w. BECKETT ATTORNEYS June 23, R w K T 2,287,595

APPARATUS FOR CONTROLLING AIR FLOW Filed Feb. 5, 1940 3 Sheets-Sheet 2 lNVENTOR REGINALD W. BECKETT ATTORNEYS June 23, 1942. R w BE KETT 2,287,595

APPARATUS FOR CONTROLLING AIR FLOW Filed Feb. 5 1940 3 Sheets-Sheet 3 INVENTOR ATTORNEYS QVHREGJNALD w. BEGKETT Patented June 23, 1942 UNITED STATES PATENT OFFICE APPARATUS FOR (ONTROLLING AIR 12 Claims.

This invention relates to oil burners, and more particularly to an improved method of and apparatus for controlling the flow of combustion air through the burners. The present application is a continuation in part of my copending application Serial No. 188,731, filed February 4,

It is an object of the invention to provide a generally improved burner having improved operating characteristics that make it more efficient and economical.

Another object of the invention is to provide an oil burner having an improved air control for regulating the admission of air to be used for combustion. More specifically, the invention aims to provide an oil burner having air inlet control means which can be adjusted to secure the optimum burner performance.

A still further object of the invention is to provide an improved method of and apparatus for regulating the flow of combustion air into and through an oil burner so that, while providing an adequate supply of oxygen to support combustion, the flow of air through the burner is reduced when the latter is notin operation.

A still further object is to providea fuel burner having a generally improved appearance and performance, which is relatively simple in design and construction, and inexpensive to manufacture.

Other objects and advantages will become apparent from the following detailed description of suitable embodiments of the invention made.

in connection with the accompanying drawings, in which like parts throughout the several views are indicated by the same numerals of reference.

Figure 1 is a side elevational view, partly in section and with parts removed, showing a burner embodying the invention connected to a furnace. The plane of the sectioned portion of the figure is indicated at l-l of Fig. 3;

Fig. 2 is a fragmentary enlarged detail view, in plan, showing the control for the air inlet door. This view is taken substantially on the line indicated at 2-2 of Fig. 1;

Fig. 3 is a rear elevational view of the burner, with parts broken away;

Fig. 4 is a front elevational view of the burner;

Fig. 5 is a fragmentary sectional view taken substantially on the line'5-5 of Fig. 1;

Fig. 6 is an enlarged fragmentary detail, in section, showing the pivotal mounting for the air inlet control door;

Fig. '7 is a detail view, with parts broken away,

showing the movable parts of the burner assem bled as a unit;

Fig. 8 is a transverse vertical sectional View, with parts removed, taken substantially on the line 88 of Fig. 1;

Fig. 9 is a fragmentary sectional view showing a modification of the invention having a counterweighted closure;

Fig. 10 is a fragmentary elevational detail showing a further modification in which a spring is employed to retain the air inlet control door in open position; and

Fig. 11 is a fragmentary sectional detail taken substantially on the line Il-H of Fig. 10-.

Referring to the drawings by numerals of reference, which indicate like parts throughout the several views, the burner comprises a pedestal or base, indicated generally by the numeral I, which is surmounted by and supports a main body portion or housing, indicated generally by the numeral 2. A horizontally disposed air or blast tube 3 is secured to the lower portion of the housing 2 at one end thereof by cap screws or studs 4 which extend through a radially di- ;;i rected flange formed at the inlet end of the air tube. On the upper portion of the housing 2 at the end thereof opposite the blast tube 3 a supporting member or bracket 5 is removably secured by cap'screws or studs 6.

The bracket 5 carries a removable unit which comprises all the movable parts of the burner including motor 1, fuel pump and pressure regulator 8, blower 9 of the sirocco type, and cover plate Ill. The blower 9 is actuated and supported by shaft l2 of the motor 'I which also actuates the fuel pump. The circular cover plate 10 has a running or clearance fit on the shaft l2 between the motor. I and blower 9.

The blower 9 is received in a chamber l4 formed in the upper portion of the housing 2 and forces air downwardly through a throat I5 tangentially into inlet end I6 of combustion air passageway I1 extending longitudinally through the bottom of the housing 2 and the air tube 3.

The fuel pump and pressure regulating device 8 draw liquid fuel through supply conduit l8 and force it under relatively high pressure through fuel pressure conduit 19 having a flexible loop 20 into fuel pipe 2| supported by bracket 22 and spider 23 in the air tube 3. A vaporizing or spray nozzle 25- is secured on the end of the fuel pipe 2| at the discharge end of the air tube 3 so that its outlet orifice 26 is disposed substantially in the plane of the smallest cross-sectional area portion of a burner head 21, to be later described. Air forced through the passageway I! by the blower 9 and moving in a helical path commingles with the oil spray emerging from the nozzle orifice 26 to form a mist of finely dispersed oil particles which burn in combustion chamber 28 of a heating unit such as a domestic furnace.

The housing 2 is symmetric in external appearance and of generally ovate form as viewed from either end. It is carried in an upright position on the base I, being of a materially greater height than width and of a materially greater width than length. The housing is of substantially uniform length from top to bottom and has a top wall t l of generally rounded form merging into relatively straight verticalside walls 3| and 32. Inwardly curving or rounded bottom walls 33 and. 34 extend downwardly as continuations of the side walls 3| and 32 and terminate in a downwardly directed socket 35, to i be later described. Rear end wall 36 carries the bracket which supports the, removable motor unit, and front end wall 31 carries the air tube 3* as mentioned above.

The blower chamber M (Fig. 8) is of the form commonly employed with rotary blowers of the sirocco type have axially extending blades, and is partially defined by a curved internal wall or partition 33 which extends between the end walls 36 and 3'! of the housing 2 from a point 39 where it is formed into the top wall 36. of the housing at substantially the center thereof downwardly to the left in a circular fashion and then to the right, as viewed in Fig. 8. The lower end of the wall 33 extends beyond the middle of the housing and to cutoil 42] of the throat I5. The radial space between the peripheral margin of the rotary margin of the rotary blower 9 and the walls of the chamber l4 progressively increases from the cutoff 40 in a clockwise direction around the rotational axis of the blower substantially to the throat l5. This increase. in the free radial crosssectional area of the housing available for the flow of air is in the direction of rotation of the blower rotor 9, indicated by the arrow of Fig, 8.

One side of the inlet end I 6. of the passage, opposite the throat I5, is defined by an internal wall or partition 42 which starts substantially at the bottom center of the housing 2 where it is connected to the lower part of the bottom wall 33, as indicated at 43, and is then. curved upwardly to the left and. then to the right in a clockwise direction following the general curvature of the passage I! as defined by the tube 3. The upper end of the partition 42 and the lower end of the partition 33 are joined by a short, vertically disposed partition 44 which partially defines the throat IS. The partition 42 i curved or sloped longitudinally of the inlet portion l6 of the air passage. This curvature is progressively increased from the lower portion 43 to the top portion where the partition 42. joins the vertical partition 44. The margin 45 of the partition 42, adjacent the end wall 36 of the housing 2, progressively approaches the axis of the. air passage ll, while the margin 46. of the partition 42, adjacent the end wall 37. of the housing, remains substantially flush with the internal wall of the air tube 3.

Tube 3 is substantially. circular in cross section. throughout its length and has a portion 4! of cylindrical form and. uniform diameter adjacent the housing 2 which merges into a tapering portion 48, which extends toward the discharge end of the tube where a second cylindri- 27 and circumferentially abuts against the annular collar or thickened section 59 on the discharge end of the tube 3. A pair of screws G3 extend through suitable drill holes inv the flange 53v and are threadedly secured in the collar to clamp the head El in heat exchanging circumferential contact with the collar.

Another pair of screws 5! extend through an annular holding ring 52, disposed about the head 21, through the flange 53 and are threadedly received in the annular thickened collar portion 5.9. at the discharge end of the tube 3. The ring 52 and flange 53. preferably have substantially the same outside diameter and the ring is axially movable over an external cylindrical portion 54 of the head 2'! which. extends forwardly from the base of the flange 5?, Between the ring 52 and flange 53, and seating on the cylindrical portion 54 of the head, is an annular ring 5-25 of fireproof fibrous material such as asbestos. This ring is clamped between the holding ring 52 and flange 53 by the screws 5| which a so hold the head 27 to the tube 3.

The head 21 is formed to present a substantially continuous circular shoulder 56 to the ad vancing air and effects an agitation thereof which is beneficial in forming a suitable combustible mixture with the fuel oil. This shoulder 56 is adjacent the small diameter cylindrical portion 49 of the passageway I? in which i located the spider 23, From the shoulder 56 the head 2'! is tapered and the internal walls thereof converge to provide a progressively decreasing, substantially circular cross-sectional area in the direction of. air flow. At substantially the region of smallest cross-sectional area the head 21 is formed with a shoulder 5'5 which further turbulates or agitates the moving air. From the shoulder 5! to the extreme end of the head 27 there is an outwardly tapering outlet or mouth 58.

A downwardly sloping passage or drill hole 59 extends through the bottom wall of the head 21 from the inside thereof between the annular shoulders 56 and 51, through a depending boss 60 integral with the head. to the foremost edge of the head. This hole serves as a drain for fuel oil that may drip from the nozzle 25 and directs the same into the combustion chamber 23. Preferably the end of the hole 59 inside the head is enlargedv or dished to more effectively drain off the oil.

The bracket 22 which holds the fuel pipe 2| has a curved or cylindrical bottom surface 64 which corresponds in curvature to the internal cylindrical surface of the portion ll of the tube This curved surface 64' assists in aligning the bracket in the air passageway El and affords a snug fit between the bracket and tube. The bracket is held in place by a depending threaded stud- 65 which extends through an elongated slot 66 formed in the bottom of the cylindrical portion 4? 01" the airtube 3; Preferably, the stud (i5 is made separately from the bracket 22. and threadedly secured therein. Accordingly, the bracket 22 may be adjusted longitudinally in the tube. 3 so as to vary the position of th nozzle 25 with respect to the head 21. A nut 91 on the stud 65 locks the bracket in adjusted position and the novel shape of the tube 3 which provides a cylindrical portion for holding the bracket 22 retains the fuel pipe 2! centered in the air passageway I1 in all positions of adjustment. The cylindrical portion 49 at the discharge end of the air tube which has a uniform internal diameter permits the spider 23 to move longitudinally in the passageway I1 while the ends of the spider legs maintain sliding engagement with the walls of the tube. Thus both ends of the fuel oil pipe 2I are supported and retained centrally in the air passageway I1 regardless of the movement of the bracket 22 and spider 23 in adjusting the nozzle 25.

A pair of ignition electrodes 99 and 99 are disposed longitudinally through the passageway I1 slightly above and on opposite sides of the oil pipe 2I. These electrodes are mounted in porcelain insulators 19 held in a clamp 1| on the top of the bracket 22. The forward ends of the electrodes 68 and 99 are directed toward one another in the region of the orifice 29 of the nozzle 25 so that a spark across the electrodes ignites the atomized fuel.

A transformer, carried in a box 13 disposed against the rear end wall 36 of the housing, furnishes high tension current to the electrodes 98 and 69. Conductors 14 enclosed by insulators extend into the inlet end It of the air passageway I1 from the transformer box 13 through an opening 11 formed in the rear wall 36 of the housing which is normally covered by the transformer box 13. Each of the conductors is provided with a springlike brush 19 formed of suitable sheet metal such as bronze or brass and which extends upwardly and at right angles across the axes of the electrodes 98 and 99.

Electrical contact is made between the brushes 19 and the electrodes by means of contact sleeves slidably received on the electrodes and urged toward the brushes 18 by helical compression springs 89. Each of the springs 89 has one end adjustably retained on the electrode by a re duced diameter portion which grips the electrode, and a nut which is threaded onto the electrode.

The transformer box 13 has a fiat plate 85 which is arranged to cover the opening 11 in the rear end wall 35 of the housing 2. Flange portions 86 and 81 of the plate 95 extend beyond the sides of the box 13 and are utilized in attaching the box to the housing. The flange 99 has a vertically disposed piano type hinge 88 secured thereto by suitable means such as spot welding. The flange 81 of the plate 95 is se- Cured to the housing 2 and an ear 9| by fillister head screws 92 (Fig. 1).

Air is drawn into the burner by the blower 9 through a downwardly directed inlet opening in a hood 94 formed on the front wall 31 of the housing 2. An air chamber 95 in the hood 94 communicates with the blower chamber I4 through a circular opening 99 formed in the front wall 31 and concentric with the shaft I2 of the blower and motor.

An air gate 91 is mounted off center on reduced diameter pins 98 (Fig. 6) of adjustable pivot screws 99 which are threadedly carried in aligned holes through the side walls of the hood 94. The screws 99 preferably have enlarged knurled heads I99 on the outside of the hood 94 so that they may be adjustably screwed toward or away from one another and shoulders I9I thereof may be made to frictionally engage apertured pivot brackets I92 which are secured to the air gate 91 to support the same and are received on the pin ends 98 of the pivot screws. Thus, by tightening the screws against the brackets I92 the gate 91 may be retained in either opened or closed or in intermediate adjusted position, as desired, to regulate the flow of air through the burner. Upon loosening the screws 99, the gate 91 is freely pivoted and falls by gravity to close the inlet opening into the hood except when held in open position by air pressure.

An adjusting rod I94 is vertically disposed in the air chamber 95 and rotatably journaled in a drilled hole in the top of the hood 94. An enlarged knurled head I95 is secured on the top of the rod I94 above the hood 94 so that the rod can be manually rotated. An indexing pin I99 extends through the rod I94 and extends radially therefrom. This pin rides in a recess I91 formed in the top of the hood 94 and having approximately a opening therein so that the rotational movement of the rod I94 is limited to about 90. The rod I94 is urged downwardly by a helical compression spring I98 which seats on a washer I99 secured on the rod I94 and a washer II9 bearing upwardly against the inside of the top wall of the hood 94.. A foot III is formed at the bottom of the rod I94 by bending the latter substantially through 90. This foot is disposed a short distance above the air gate 91 when the latter is closed and it is preferably provided with a rubber covering II2 to silence the contact between the foot and the gate when the movement of the latter is arrested by the foot. When the pivot screws 99 are loosened so that the air gate 91 is free to pivot on the pins 98, the gate is opened by the air pressure on the underside thereof when the blower 9 is rotating. The amount that the air gate will open under the influence of air pressure can be varied or adjusted by rotation of the rod I94 which moves the foot III to various positions. For example. when the rod is rotated to its extreme counterclockwise position as viewed in Fig. 2 and as limited by the pin I99 in the recess I91, the gate 91 will be able to open only a minimum amount whereas movement of the rod I94 to its extreme clockwise position as viewed in Fig, 2 will carry the foot III to a position substantially parallel with the axis of the pivot screws 99 and a maximum opening of the gate 91 is permitted. In this manner, by means of the rod I94 the opening of the gate 91 which regulates the quantity of air forced through the passageway I1 by the blower 9 can be adjusted while the burner is in operation to give the most efficient and desirable type of flame in the combustion chamber 28. The frictional effects of the pin I99 and spring I93 are adequate to temporarily hold the rod I94 while adjustment of the burner is being made. After the adjustment is complete the rod I94 is locked in position by set screw II4. As long as the blower 9 is in operation the gate 91 is held open against the foot III of the adjusting rod I94. Upon shutting off the burner so that the blower 9 stops, the air gate 91 drops by gravity to the closed position illustrated in Fig. 1. Downward pivotal movement of the gate 91 is limited by a suitable stop II3, Fig. 5, or by engagement of the edges thereof which are parallel to the axis of the pivot screws 99 with the inside bottom edge of the wall of the hood 94 or the end Wall 31 of the housing 2.

The movable parts of the burner are carried by a substantially U-shaped cradle I I secured to the floor of the supporting member or bracket 5 by studs H5 and centered thereon by raised tracks or bosses II1 (Fig. 3). The upstanding arms of the cradle II5 are provided with metal bands H3 which confine annular rubber rings or cushions (not shown) embracing the journal bosses on the bells of the motor 1. Accordingly, the motor, blower, and pump are resiliently cushioned and the single rotating shaft is supported intermediate its ends at a plurality of points by rubber cushioned journals.

An upright portion I I9 of the supporting member 5 is disposed against the upper portion of the rear wall 33 of the housing 2 and a circular opening I 29 is formed through the portion I I9 and the wall 36 to permit passage of the blower 9 when removing or replacing the movable parts or motor drive unit. This opening is closed by the cover plate I9 which is secured to the portion I IQ of the bracket 5 by screws I2I (Fig. 3).

The pedestal or base I has a relatively large footing portion I24 which affords a wide area support for the burner. Square or rectangular pads or cushions I33 are received in sockets I39 at marginal portions of the footing portion I24 of the base. Preferably, the pads I33 are three in number and formed of resilient cushioning or vibration-absorbing material such as wood, cork, or rubber, thus effecting a quieting three point mounting for the burner. In the event that the surface on which the burner is to be supported is irregular or of uneven height, the pads I33 can be made shorter or longer, as required, so as to carry the base I evenly and firmly. Upwardly directed wall portions I25 formed integrally at the central portion of the front end of the base are surmounted by a substantially horizontally disposed platform portion I25. This platform is thus disposed a material distance above the surface on which the footing portion I24 of the base rests. A vibration absorbing block I21 formed of suitable material such as wood or cork is carried on the platform portion I26 and is surmounted by the housing 2. Preferably, the block I21 fits into the socket 35 formed in the bottom of the housing so that the top sides of the block are embraced by depending portions I28 of the socket. Similarly, the upwardly directed walls I25 of the base extend above the level of the platform I29 to embrace the bottom sides of the block I21.

In plan form the block I21 is non-circular in shape, preferably being square or rectangular. The depending portions I28 of the socket 35 are formed to a corresponding shape as are also the upwardly projecting portions of the walls I 25 of the base so that when the block I21 is properly seated on the platform I26 and in the socket 35 the burner housing 2 is correctly aligned with respect to the base I.

A stud I29 is secured in the central portion of the socket 35 and extends downwardly through an aperture in the center of the block I21 and has a loose fit in the central hole formed in the platform I 26. The parts are drawn together by a nut I39 which forces a washer ISI of a material having the capacity to deaden vibrations, such as lead, upwardly against the bottom of the platform portion I26.

In Fig. 9 is illustrated a modification of the invention in which the air inlet control door 91 has a counterweight I99 adjustably attached thereto, as by screw I93, so that the door or shutter is substantially balanced on the pivot pins 92, there being slightly more weight to the right of the pivots, as viewed in Fig. 9, than to the left so that the door or shutter 91 normally tends to pivot downwardly in a clockwise direction to close the opening into the hood 94.

In this modification, the downward pivotal movement of the air shutter or door is arrested by a suitable stop element or pin I9I which is secured to the front wall of the hood adjacent the bottom edge thereof, as by a pressed fit into a drilled hole, or by being threaded into a drilled hole. If desired, the pin I9I may be covered by a short length of rubber tubing I92 having a frictional fit thereon, which serves as a silencer, preventing metal to metal contact between the pin and the shutter or door 91.

Figs. 10 and 11 illustrate a modification in the operation of the air inlet gate 91 when it is desired to retain the latter open at all times so that a fiow of air through the burner is permitted after the blower 9 stops. In this modification the enlarged knurled head I99 is eliminated from one of the pivot screws 99 and the latter provided with a screwdriver slot I34 for turning the same. The pivot screw is of increased length to receive on the portion thereof extending outside of the hood 94 a spring I35. One end I36 of the spring bears against the front wall 31 of the housing 2 to prevent rotational movement of the spring on the pivot screw 99 and the opposite end I31 of the spring is bent underneath the side wall of the hood 9 into engagement with the underside of the air gate 91 to urge the latter in a clockwise pivotal movement as viewed in Fig. 10 into engagement with the foot III of the adjusting rod Hi4. Accordingly, the spring I35 retains the gate 91 open as far as is permitted by the particular adjustment of the rod I94, preventing the gate from dropping by gravity to closed position when air is no longer forced through the burner by the blower 9.

The unique design of the burner housing 2 provides a wiring box I14 between the outside walls of the housing and the internal partitions 38 and 42. A removable plate or plates I8I held in place by a screw or screws I15 secured in a boss I19 formed on the partition wall 38 close the opening in the side wall 3| leading into the terminal or wiring box I 14. Thus, but a single electrical conduit I11 leads to the burner and enters the wiring box I 14 through a fitting I18 in the removable side wall plate 3|. The power leads I19 to the transformer extend through a cored hole I89 (Figs. 3 and 5) in the rear wall 36 of the housing and the power leads I82 to the motor 1 pass through a cored hole I33 extending through both the rear wall 39 of the housing and the upright portion N9 of the bracket 5. Accordingly, the wiring leads for the burner are substantially concealed and protected from injury.

The fuel pressure conduit I9 extends through a slot I84 formed in the rear wall 36 of the housing and which is formed radially from the opening 11. Accordingly, when the transformer box 13 is pivoted to open position, the conduit I 9 may be readily removed longitudinally through the passage I 1 and out the opening 11 merely by sliding it out of the slot I84. Preferably, a rubber grommet (not shown) fits around the conduit I9 in the slot I84 to prevent the flow of air therethrough and wear of the conduit on the walls of the slot.

The arrangement for controlling the admission of air to the burner is advantageous in that the amount of air flowing when the blower is in operation can be regulated while the burner is operating, so that maximum operating efliciency of the burner can be quickly established. Additionally, the air inlet gate can be readily converted, from the type which remains open a predetermined amount at all times whether the burner movement about a substantially horizontal axis so that entering air lifts the gate to open the inlet, an adjustable rod extending through the housing in a generally vertical position and having one end disposed above the gate to engage the latter and thereby limit the pivotal movement of the gate, and resilient means for yieldproviding a blower chamber and a blower in the chamber, means providing an air inlet opening for said chamber disposed in a generally horizontal position so that air entering into the housing flows in a generally vertical direction through the opening, a gate and means mounting the same for pivotal movement across said opening from a normal position in which the gate is generally horizontal to close the opening to an upright position in which the gate is displaced from the opening, whereby the force of inf-lowing air displaces the gate from normal position and the movement of the center of gravity of the gate toward the pivot axis thereof during said displacement effects a reduction in the air force required to move the gate, and means limiting the displacement.

2. In an oil burner having a housing structure providing a blower chamber, a blower in the chamber, means defining an air inlet opening for the chamber, a pivoted gate normally disposed across the opening to close the same and displaceable by the force of air entering the chamber, and means for limiting the displacement comprising a substantially vertical rod rotatably mounted in the housing and having a lateral extension formed thereon whereby rotation of the rod moves the extension over an arc to different operative positions, friction means for yieldingly holding the rod in different rotative positions, and screw means for locking the rod in one of said positions.

3. In an oil burner having a pivoted air inlet gate, a rotatable rod adjustable to different positions for limiting the movement of the gate, spring pressed friction means for yieldingly holding the rod in adjusted position, and screw means having connection with the rod for locking the same in adjusted position.

4. In an oil burner having a housing structure providing a blower chamber and an inlet through which air flows upwardly to enter the housing, a gate disposed across said inlet to normally close the same, means mounting the gate for pivotal movement about a substantially horizontal axis so that entering air lifts the gate to open the inlet and whereby the center of gravity of the gate is shifted toward said axis, and means limiting the pivotal movement of the gate.

5. In an oil burner having a housing structure providing a blower chamber and an inlet through which air flows upwardly to enter the housing, a gate disposed across said inlet to normally close the same, means mounting the gate for pivotal ingly holding the rod in adjusted position.

6. In an oil burner having a housing structure providing a blower chamber and an inlet through which air flows upwardly to enter the housing, a gate disposed across said inlet to normally close the same, means mounting the gate for pivotal movement about a substantially horizontal axis so that entering air lifts the gate to open the inlet, an adjustable rod extending through the housing in a generally vertical position and having one end disposed above the gate to engage the latter and thereby limit the pivotal movement of the gate, and a set screw threaded into the housing and having connection with the rod to lock the latter in adjusted position.

'7. In an oil burner having a housing structure providing a blower chamber and an inlet through which air flows upwardly to enter the housing, a gate disposed across said inlet to normally close the same, means mounting the gate for pivotal movement about a substantially horizontal axis so that entering air lifts the gate to open the inlet, an adjustable rod extending through the housing in a generally vertical position and having one end disposed above the gate to engage the latter and thereby limit the pivotal movement of the gate, resilient means for yieldingly holding the rod to facilitate manual adjustment of the same in regulating the air inlet, and threaded means carried by the housing and having connection with the rod to lock the latter in adjusted position.

8. In an oil burner having a housing structure providing a blower chamber and an air inlet through which air flows to enter the chamber,

- a pivoted gate normally disposed across the inlet to close the same and movable by the force of entering air to open the inlet, an adjustable rod extending through the housing and rotatable therein to difierent positions for limiting the movement of the gate, a recess formed in the casing adjacent the rod and provided with spaced shoulders, and means carried by the rod and movable in the recess between the shoulders to indicate the position of the rod relative to the gate and to limit the movement of the rod by interengagement with said shoulders.

9. In an oil burner having a housing structure providing a blower chamber and including a downwardly directed hood having a bottom air inlet communicating with the chamber, a gate and means mounting the same in the inlet for pivotal movement about a substantially horizontal axis so that the force of air entering the housing through the inlet lifts the gate, a rotatable rod extending downwardly through the top of the housing and the hood and having a foot portion disposed above the gate to engage the latter and thereby limit the movement of the gate, means on the rod externally of the housing for rotating the rod about a substantially vertical axis to thereby shift the position of the foot portion, and means for holding the rod in rotated position.

10. In an oil burner having a housing structure providing a blower chamber and an air inlet through which air flows to enter the chamher, a gate normally disposed across the inlet to close the same, and means mounting the gate for pivotal movement, said means comprising an apertured element on the gate and a pivot screw threaded through the housing, said screw having a reduced diameter end receivable in the aperture of the element and having a shoulder engageable with the element upon tightening of the screw to frictionally hold the element and the gate in fixed position in the air inlet.

11. In an oil burner having a housing structure providing a blower chamber and an air inlet through which air flows to enter the chamber, a gate normally disposed across the inlet to close the same, means mounting the gate for pivotal movement, said means comprising an apertured element on the gate and a pivot screw threaded through the housing, and spring means carried by the screw and engageable with the gate to yieldingly hold the latter in predetermined position.

12. In an oil burner having a housing providing a blower chamber and hood means on the housing forming an air inlet opening across the underside of the hood, a blower in the chamber and means for actuating the same to draw air upwardly through said opening and into the burner, an air gate and means pivotally mounting the same in the hood means for turning movement about a substantially horizontal axis to normally gravitate to a position across said opening to close the latter, said gate being so mounted that the pressure thereagainst of air drawn into the burner raises the gate to open position and the center of gravity of the gate moves toward said axis so that less air force is required to retain the gate in open position than to initially raise the gate and whereby the gate remains substantially stationary in open position during slight fluctuations in the pressure of the air flowing into the burner, and adjustable means engageable with the gate for limiting the turning movement of the latter during the raising thereof to open position, said last named means being movable to alter the open position of the gate whereby to control the flow of air into the burner.

REGINALD W. BECKETT. 

